On Counter-Adversarial Resilience in Permeable Networked Systems

In recent years, a flood of devices has permeated our personal and professional lives, with increasingly interconnected networks playing an ever-growing role in day-to-day activities. As these systems expand in both importance and complexity, their value to attackers and their attack surface simultaneously increase. In this dissertation, I argue that traditional defensive approaches fail to acknowledge this changing landscape. Instead, by focusing on the twin concepts of permeable networks and counter-adversarial behavior, defenders will be able to achieve better outcomes. The dependencies, interactions, and relationships among the growing corpus of connected devices create complex systems that are difficult for both users and operators to reason about. Consequently, despite heightened awareness of security risks, the rate and scale of data breaches continue to accelerate. This underlying complexity renders networks {permeable} to attackers. In parallel, interest in low- and no-trust distributed computing, such as federated learning, ad hoc networking, and blockchain systems, has been on the rise. In these contexts, users and devices interact cooperatively toward common goals while contending with potentially adversarial participants. Inherently permeable, these cooperative systems benefit from adopting counter-adversarial behaviors. By discarding the traditional goal of strict prevention, defenders can shift their focus to {counter-adversarial} behaviors instead. These behaviors aim to limit attackers' choices, exhaust their resources, or reduce their effectiveness, collectively disincentivizing attacks. This dissertation leverages these dual concepts to explore counter-adversarial behaviors in the context of permeable networked systems. It further describes methods such as information partitioning, ensemble fusion, and resilience analysis that enable novel counter-adversarial strategies. In doing so, this dissertation provides solutions to the challenges faced by increasingly prevalent permeable systems. Collectively, these form a foundation for the development of more resilient communication architectures.